An increasing variety of lighting applications require a precisely controlled spectral characteristic of the radiant energy. It has long been known that combining the light of one color with the light of another color creates a third color. For example, the commonly used primary colors Red, Green and Blue of different amounts can be combined to produce almost any color in the visible spectrum. Adjustment of the amount of each primary color enables adjustment of the spectral properties of the combined light stream. Recent developments for selectable color systems have utilized light emitting diodes or other solid state light sources as the sources of the different light colors.
Light emitting diodes (LEDs) for example were originally developed to provide visible indicators and information displays. For such luminance applications, the LEDs emitted relatively low power. However, in recent years, improved LEDs have become available that produce relatively high intensities of output light. These higher power LEDs, for example, have been used in arrays for traffic lights. Today, LEDs are available in almost any color in the color spectrum.
Additionally, for many lighting applications, an LED based fixture incorporates a circuit board supporting and providing electrical connections to a number of individually packaged LEDs. Often the LEDs are arranged in a fairly tight matrix array (see e.g. U.S. Pat. No. 6,016,038), although a variety of other arrangements are known. For example, U.S. Pat. No. 6,995,355 to Rains, Jr. et al. discloses lighting systems using circular or linear arrangements of LED sets as well as rectangular matrix arrangements and other position patterns. In the noted examples, the sets of LEDs have included LEDs configured for emitting different individual colors or wavelengths (e.g. red, green and blue), although the U.S. Pat. No. 6,995,355 patent also suggests inclusion of white LEDs or other white light sources. The red, green and blue light allows adjustment and control of the character of the combined light emitted by the system. As the quality of white LEDs continues to improve, newer lights will utilize similar arrangements of LEDs where all or some the LEDs are white LEDs. Even with white light systems, some implementations use multiple colors and light mixing to provide color temperature adjustment.
It is well known that many different combinations of wavelengths can produce the same perception of color, and that “Chromaticity” has been long been used to describe the perceived color of a visual stimulus of a human. Many models have been used describe Chromaticity. In one implementation, the CIE system characterizes a given visual stimulus by a luminance parameter Y and two chromaticity coordinates x and y that specify a particular point on the well-known chromaticity diagram. The CIE system parameters Y, x and y are based on the spectral power distribution of the energy emission from a light source. This model also takes into consideration various color sensitivity functions which correlate generally with the response of the human eye.
Also, commonly used primary colors Red, Green and Blue of different amounts can be combined to produce almost any color in the visible spectrum in a lighting system. These colors can be represented by the CIE tristimulus values, commonly referred to as X, Y, and Z, respectively, and as illustrated by FIG. 16. Thus, the CIE xyY coordinates may be converted to CIE XYZ coordinates for controlling aforementioned LEDs using the following equations:
                    X        =                              x            y                    ⁢          Y                                    (                  Eqn          .                                          ⁢          A                )                                Y        =        Y                            (                  Eqn          .                                          ⁢          B                )                                Z        =                                            1              -              x              -              y                        y                    ⁢          Y                                    (                  Eqn          .                                          ⁢          C                )            
However, LEDs have different operating characteristics such that no two LEDs are producing the identical color of light or intensity. If mass producing light fixtures that produce combined light, it is conceivable that no two light fixtures are able to produce the same light for all input settings. Hence, a need exists for a way to validate input settings to an LED fixture so as to avoid generating unintended light, and to perform the task in an efficient manner that can be implemented on a large production scale. Preferably, such a technique should offer an increased degree of responsiveness to user inputs.